ANTIBIOTICS

1. ANTIBIOTICS 2012

2. ANTIBIOTICS • Antimicrobial drugs (ATBs) • effective in the treatment of infections • Selective toxicity • the ability to kill an invading microorganism without harming the cells of the host • advantage of the biochemical differences that exist between microorganisms and human beings. • Selective toxicity is relative • it is necessary to control the concentration of ATB • to attack the microorganism while still being tolerated by the host. • Selective antimicrobial therapy • ATB choice according sensitivity of bacteria.

3. Mechanism of action Inhibition of cell wall synthesis Penicillins Cephalosporins Monobactams Vancomycin Inhibition of DNA gyrase: Quinolones RNA polymerase Rifampicin Inhibition of protein synthesis: Aminoglycosides Tetracyclines Erythromycin Chloramphenicol Inhibition of folic acid Trimethoprim metabolism: Sulfonamides

4. ATBs therapy • The choice • of appropriate antibacterial drug • The dose and route of administrations • The duration of therapy • Monitoring • patient must be informed • especially about adverse effects - compliance

5. 1. The choice of appropriate • Diagnosis of infection • community x hospital infections, acute vs chronical • broad-spectrum antibiotics for empirical therapy, • narrow-spectrum antibiotics for selective treatment or outpatients • Patients factors • age, sex (pregnant, lactating women), • weight, allergies, genetic factors, • renal and hepatic function, • concurrent medication • Drug factors • antibacterial spectrum (narrow-spectrum, broad-spectrum activity, Gram-positives Gram-negatives), cidal vs. static • pharmacokinetics – to infection site, • adverse effects, drug interactions, convenience, cost

6. Diagnosis of infection • Empirical th • community • Narrow spectrum - rely on localization and signs • hospital infections • Broad spectrum reserved ATB • Targeted th • Chronical infections • E.g. „Diabetic leg“, TBC

7. Patients factors • age, weight, • allergies, genetic factors, • Type B AE - • sex (pregnant, lactating women), • Type D AE - • renal and hepatic function, • Type A AE - • concurrent medication • Interactions -

8. Drug factors • Cidal vs. Static • antibacterialspectrum • (narrow-spectrum, broad-spectrumactivity, Gram-positives Gram-negatives), • pharmacokinetics • Route of administration, penetration to infectionsite, • adverseeffects, druginteractions, convenience, cost

9. Bacteriostatic vs. bactericidal drugs • Bacteriostatic • arrest the growth and replication of bacteria • at serum levels achievable in the patient - limit the spread of infection while the body's immune system attacks, immobilizes, and eliminates the pathogens. • If the drug is removed before the immune system has scavenged the organisms, enough viable organisms may remain to begin a second cycle of infection. • Intact immune system • decreased e.g. in: alcoholism, diabetes, immunosuppresion, malnutrition, advanced age - bactericidal agents are required. • Bactericidal • kill bacteria at drug serum levels achievable in the patient. - often drugs of choice in seriously ill patients. • It is possible for ATB to be bacteriostatic for one organism and bactericidal for another.

10. Bacteriostatic vs. bactericidal drugs: • Minimum inhibitory concentration (MIC) • the lowest concentration of ATB that inhibits bacterial growth. Effective antimicrobial therapy • ATB concentration in body fluids should be greater than the MIC. • Minimum bactericidal concentration (MBC) • the lowest concentration of ATB that results in a 99.9 % decline in colony count after overnight broth dilution incubations. • MIC/MIB • It is an in vitro test in a homogenous culture system, while in vivo: • plasma concentration should reach a value several-times higher (8x) • concentration at the site of infection may be considerably lower than the plasma concentration. • it is necessary to take into consideration pharmacokinetic properties of antibiotics • penetration into site of infection, its metabolism..

11. Classification of antibacterial agents: bactericidal bacteriostatic β-lactam agents Erythromycin Aminoglycosides Tetracyclines Co-trimoxazole Chloramphenicol Vancomycin Sulfonamides Trimethoprim

12. Chemotherapeutic spectra • Narrow spectrum • only against a single or a limited group of microorganisms, • e.g. INH is active only against mycobacteria. • Extended spectrum • against G+ organisms and also against a significant number of G- bacteria • e.g., ampicillin • Broad spectrum • e.g. tetracycline and chloramphenicol • affect a wide variety of microbial species. • !!! alter the normal bacterial flora • precipitate a superinfection of an organism, e.g., candida.

13. Combinations of antimicrobial drugs • It is better to treat patients with the single agent • that is most specific for the infecting organism. • reduces the possibility of superinfection, • decreases the emergence of resistant organisms • minimizes toxicity. • Combination • Special situations • e.g., the treatment of tuberculosis, sepsis

14. Combinations of antimicrobial drugs • Advantages - Synergism • e.g., b-Iactams and aminoglycosides – synergism – rare example • multiple drugs used in combination indicated only in special situations (e.g., infection is of unknown origin). • Disadvantages – AE may multiply • Hepatotoxity of anti-TBC • Therapy failure static vs cidal • (e.g. TTC X PNC or cephalosporins)

15. Complications of antibiotic therapy • Hypersensitivity– type B • Direct toxicity – type A, B • Superinfections – type A • Resistance – primary, secondary, cross-

16. Drug resistance • growth of bacteria is not halted • by the maximal level of that antibiotic that can be tolerated by the host. • Primary • Some organisms are inherently resistant to an antibiotic • e.g., gram-negative organisms are inherently resistant to vancomycin. • Secondary • spontaneous mutation or acquired resistance and selection. • Cross-resistance • resistant to more than one antibiotic.

17. PK - Pharmacokinetics • concentration at site of infection vs. infection type and severity • CNS, placenta, bones, teeths • absorption – distribution - elimination

18. 2a. ROUTE OF ADMINISTRATION • Oral route • mild infections, outpatient basis. • If i.v. therapy initially • switch to oral agents occurs as soon as possible. • Parenteral administration • drugs that are poorly absorbed from GIT, • e.g., vancomycin, the aminoglycosides, amphotericin • treatment of serious infections.

19. 2b. RATIONAL DOSING • based on their: • pharmacodynamics • Sign of infections • time-dependent killing • pharmacokinetics • concentration-dependent killing - TDM • post-antibiotic effect.

20. Concentration-dependent killing • aminoglycosides, fluoroquinolones • significant increase in the rate of bacterial killing as the concentration of antibiotic increases from 4- to 64-fold the MIC of the drug for the infecting organism. • bolus infusion achieves high peak levels, • favoring rapid killing.

21. Time-dependent killing • beta-lactams, glycopeptides, macrolides, clindamycin • killing effect is best predicted by the percentage of time • that blood concentrations of a drug remain above the MIC. • increasing the concentration of ATB to higher multiples of the MIC does not significantly increase the rate of kill • E.g., for PNC and cephalosporins, dosing schedules that ensure blood levels greater than MIC for 60 – 70 % of the time was showed to be clinically effective. • severe infections are best treated by continuous infusion • of these agents rather than by intermittent dosing.

22. Post-antibiotic effect (PAE) • A persistent suppression of microbial growth that occurs after levels of antibiotic have fallen below the MIC. • Antimicrobial drugs with a long PAE (several hours) often require only one dose per day. • E.g., aminoglycosides and fluoroquinolones, particularly against gram-negative bacteria.

23. PROPHYLACTIC ANTIBIOTICS • the use of ATB for the prevention • risk of bacterial resistance and superinfection • benefits mustoutweigh the potential risks/AE. • Examples • Prevention of streptoccocal infections • in patients with history of rheumatic heart disease. Patients may require years of treatment. • Pretreatment of patients undergoing dental extractions • who have implanted prosthetic devices (e.g., artificial heart valves) to prevent seeding of the prosthesis. • Prevention of tuberculosis or meningitis • in those who are in close contact with infected patients.

24. ATB - MA CELL WALL CELL MEMBRANE DNA Inhibitors of cell membrane function THFA Ribosomes Isoniazid Amphotericin B mRNA PABA Inhibitors of nucleic acid function or synthesis Inhibitors of protein synthesis Inhibitors of cell wall synthesis Inhibitors of metabolism Tetracyclines Aminoglycosides Macrolides Clindamycin Chloramphenicol Fluoroquinolones Rifampin b-Lactams Vancomycin Sulfonamides Trimethoprim (according to Lippincott´s Pharmacology, 2009)

25. Summary of antimicrobial agents affecting cell wall synthesis Agents affecting the cell wall b-lactamase inhibitors Clavulanic acid Sulbactam Tazobactam Other antibiotics b-lactam antibiotics Bacitracin Vancomycin Daptomycin Penicillins Carbapenems Monobactams Cephalosporins Ertapenem Imipenem/cilastatin* Meropenem Amoxicillin Ampicillin Dicloxacillin Indanyl carbenicillin Methicillin Nafcillin Oxacillin Penicillin G Penicillin V Piperacillin Ticarcillin Aztreonam 2nd generation 1st generation 4th generation 3rd generation Cefadroxil Cefazolin Cephalexin Cefaclor Cefprozil Cefuroxime Cefoxitin Cefdinir Cefixime Cefotaxime Ceftazidime Ceftibuten Ceftizoxime Ceftriaxone Cefepime (according to Lippincott´s Pharmacology, 2009)

26. INHIBITORS OF CELL WALL SYNTHESIS • Bactericidal • selectively interfere with synthesis of the bacterial cell wall • a structure that mammalian cells do not possess. • The cell wall is a polymer called peptidoglycan • that consists of glycan units joined to each other by peptide cross-links. • require actively proliferating microorganisms • To be maximally effective, these agents • Little or no effect on bacteria that are not growing • do not combine with bacteriostatic ATBs

27. PENICILLINS Penicillin G • 1928, A. Fleming • Of most widely effective ATBs and also the least toxic drugs known • increased resistance limited their use. • The nature of their side chain affects the spectrum, stability to stomach acid, and susceptibility to bacterial degradative enzymes (beta-Iactamases). • Mechanism of action • Inhibition of transpeptidase: • PNCs inhibit PBP-catalyzed transpeptidase reaction. • Production of autolysins – • G+ cocci produce degradative enzymes (autolysins - that participate in the remodeling of the bacterial cell wall). • In the presence of PNC - the degradative action of the autolysins proceeds in the absence of cell wall synthesis. • Inactive against organisms devoid peptidoglycan structure of membrane (e.g., mycobacteria).

28. Antibacterial spectrum • limited • Lower ability to cross the bacterial peptidoglycan cell walland to reach PBP • G+ • Mainly – higher permeability of CW • G- • have an outer lipopolysaccharide membrane surrounding the cell wall • a barrier to the water-soluble PNCs. • Contain water-filled channels (porins) that permit transmembrane entry. • Pseudomonas aeruginosa lacks porins, making these organisms intrinsically/primarilly resistant to many antimicrobial agents. • Note: For this reason, PNCs have little use in the treatment of intracellular pathogens.

29. NATURAL PENICILLINS (narrow spectrum) • PENICILLIN G (benzylpenicillin) • a number of gram-positive and gram-negative cocci, gram-positive bacilli, and spirochetes. • Susceptible to inactivation by beta-lactamases. • Unstable in low pH – is for parenteral therapy • PROCAINE PENICILLIN G • prolonged action, i.m. • BENZATHINE PENICILLIN G • Very long action; depo form, i.m. • PENICILLIN V • a spectrum similar to penicillin G, • not used for treatment of septicemia because of its higher minimum bactericidal concentration (MLC). • is more acid-stable than penicillin G – is for p.o.

30. Antistaphylococcal penicillins • methicillin • Oxacillin* • nafcillin, cloxacillin, dicloxacillin • penicillinase-resistantPNCs • treatmentofinfectionscaused by penicillinase-producingstaphylococci. • Methicillin-resistantstrains(MRSA) • usuallysusceptible to vancomycin • rarely to ciprofloxacin, rifampin oxacillin

31. Extended spectrum penicillins • AMPICILLIN and AMOXICILLIN • Destroyed by beta-lactamases !!! • spectrum similar to penicillin G, but are more effective against somegram-negative bacilli - Hemophilusinfluenzae, E. Coli • Widely used in the treatment of respiratory infections; • amoxicillin is employed prophylactically by dentists • for patients with arteficial heart valves who are to undergo extensive oral surgery. • Resistance • a problem because of their inactivation by plasmid-mediated penicillinase (E. coli and H. influenzae - frequently resistant). • Formulation with a beta-lactamase inhibitor (e.g. clavulanic acid, sulbactam) can protect the PNC from enzymatic action. • Ampicillin • drug of choice for the gram-positive bacillus Listeriamonocytogenes.

32. Acylureido penicillins • Piperacillin • effective against P. aeruginosa • as well as a large number of gram-negative organisms. • It is susceptible to breakdown by beta-lactamase – formulation with tazobactam. • Mezlocillin, azlocillin – similar – but currently not registered in CR • REVERSED SPECTRUM PNCs: • MECILLINAM • More potent against Gram-negative enteric bacteria, • hydrolyzed by beta-lactamases. • Pivmecillinam is a pro-drug, hydrolyzed to mecillinam.

33. Penicillins - pharmacokinetics • Route of administration determined by • the stability of the drug to gastric acid and • by the severity of the infection. • only oral formulations • Penicillin V, amoxicillin, amoxicillin+clavulanic acid are. • only parenteral • PNC G, acylureido • Depot forms: • Procaine penicillin G and benzathine penicillin G – • administered IM; serve as depot forms. • Slowly absorbed into the circulation and persist at low levels over a long time period • both • ampicillin

34. Pharmacokinetics - Absorption • incomplete • Most of PNCs after oral administration • reach the intestine in sufficient amounts to affect the composition of the intestinal flora. • amoxicillin is almost completely absorbed • it is not appropriate therapy for the treatment of salmonella-derived enteritis • therapeutically effective levels do not reach the organisms in the intestinal crypts • Absorption of PNC V and all the penicillinase-resistant PNCs is impeded by food in the stomach • they must be administered 30-60 minutes before meals or 2-3 hours postprandially. • Other PNCs are less affected by food.

35. Pharmacokinetics - Distribution • Extracellular • All PNCs cross the placental barrier (TYPE A) • but none have been shown to be teratogenic. • Penetration into certain sites is insufficient • e.g. bone or cerebrospinal fluid • Increased during inflammation. • During the acute phase (first day), • the inflamed meninges are more permeable to PNC - increased ratio in the amount of drug in CNS compared to the amount in the serum. • As the inflammation subsides, • permeability barriers are reestablished. Levels in the prostate are insufficient to be effective against infections. • Metabolism: • Host metabolism of the beta-Iactam antibiotics is usually insignificant.

36. PEN - pharmacokinetics - excretion • Kidney • tubular secretion and glomerular filtration • Patients with impaired renal function - adjust dosage regimens ! • T1/2 of penicillin G can increase from a normal of 0.5-1.0 hour to 10 hours in renal failure. • Probenecid inhibits the secretion of penicillins !! • Biliary route • Nafcillin • [Note: This is also the preferential route for the acylureidopenicillins in cases of renal failure.] • breast milk and into saliva

37. PEN - adverse reactions • PNCs are among the safest drug • Hypersensitivity – type I-IV: • The most important • The major cause is metabolite, penicilloic acid, • which reacts with proteins and serves as a hapten to cause an immune reaction. • Cca 5% of patients have some kind of reaction • from urticaria to angioedema and anaphylaxis • Cross-allergic reactions among the beta-lactam antibiotics ! • Diarrhea: • Disruption of saprophytes • Especially in agents that are incompletely absorbed or with extended spectrum. • pseudomembranous colitis may occur.

38. Adverse reactions • Nephritis • acute interstitial nephritis in high doses of methicillin. • Neurotoxicity • PNCs are irritating to neuronal tissue and can provoke seizures if injected intrathecally or if very high blood levels are reached - epileptic patients are especially at risk. • Cation toxicity: • PNCs generally administered as the Na or K salt. • Hoigné syndrom • if the suspension of PNC is by mistake injected i.v. - embolisation of pulmonary veins - tachypnea, anxiety, dyspnea • Nikolau’s syndrom • suspension of PNC by mistake i.a. - embolisation in arteries - even amputation necessary)

39. beta-lactamase inhibitors Clav. acid • clavulanic acid, sulbactam, tazobactam • containa beta lactam ring, • do not havesignificantantibacterialactivity • bindto and inactive beta-lactamases • Not all beta-Iactamases are inhibited. E.g., tazobactam (compoundedwithpiperacillin) does not affect P. aeruginosa beta-Iactamase. Therefore, thisorganismremainsrefractory to piperacillin. • AUGMENTIN (amoxycillin and clavulanic acid) • TIMENTIN (ticarcillin and clavulanic acid) • Piperacillin + tazobactam • Ampicillin + sulbactam

40. Penicillins and aminoglycosides • synergistic • enhanced antimicrobial activity • facilitate the entry of aminoglycosides • Because cell wall synthesis inhibitors alter the permeability of bacterial cells, these drugs can • should never be placed in the same infusion fluid, • the positively charged aminoglycosides form an inactive complex with the negatively charged PNCs.

41. Clinical uses of penicillins • Given p.o. - in more severe cases i.v.; often in combination with other ATB. • bacterial meningitis (e.g. by N. meningitidis, S. pneumoniae): benzylPNC, high doses i.v. • bone and joint infections (e.g. S. aureus): flucloxacillin • skin and soft tissue infections (e.g. Streptococcus pyogenes or S. • aureus): benzylPNC, flucloxacillin; animal bites: co-amoxiclav • pharyngitis (from S. pyogenes): phenoxylmethylPNC • otitis media (S. pyogenes, H. influenzae): amoxicillin • bronchitis (mixed infections common): amoxicillin • pneumonia: amoxicillin • urinary tract infections (e.g. with E. coIl): amoxicillin • gonorrhea: amoxicillin (+ probenecid) • syphilis: procaine benzylPNC • endocarditis (e.g. with Streptococcus viridans or Enterococcus faecalis) • serious infections with Pseudomonas aeruginosa: piperacillin. • This list is not exhaustive !!!

42. cephalexin Cephalosporins • b-Iactam- closely related both structurally and functionally to the penicillins. • Mostly semisynthetic - mode of action as penicillins • same resistance mechanisms -however, they tend to be more resistant than the PNCs to b-Iactamases. • Antibacterial spectrum • Classified as first, second, third, or fourth generation, • based largely on their bacterial susceptibility patterns and resistance to b-Iactamases. • ineffective against MRSA, L. monocytogenes, Clostridium difficile, and the enterococci.

43. Summary of antimicrobial agents affecting cell wall synthesis INHIBITORS OF CELL WALL SYNTHESIS b-LASTAMASE INHIBITORS Clavulanic acid Sulbactam Tazobactam OTHER ANTIBIOTIC b-LASTAMASE ANTIBIOTIC Bacitracin Vancomycin CARBAPENEMS MONOBACTAMS PENICILLINS CEPHALOSPORINS Imipenem/cilastatin Meropenem* Ertapenem Amoxicillin Ampicillin Cloxacillin Dicloxacillin Indanyl carbenicillin Methicillin Nafcillin Oxacillin Penicillin G Penicillin V Piperacillin Ticarcillin Aztreonam 3rd GENERATION 4th GENERATION 1st GENERATION 2nd GENERATION Cefadroxil Cefazolin Cephalexin Cephalothin Cefaclor Cefamandole Cefprozil Cefuroxime Cefotetan Cefoxitin Cefdinir Cefixime Cefoperazone Cefotaxime Ceftazidime Ceftibuten Ceftizoxime Ceftriaxone Cefepime (according to Lippincott´s Pharmacology, 2009)

44. Pharmacodynamics First generation: • cephalexin, cephalotin, cefazolin • act as penicillin G substitutes – G+; • resistant to the staphylococcal penicillinase; • activity against Proteus mirabilis, E. coli, and Klebsiella Pneumoniae (the acronym PEcK) . Second generation: • Cefuroxime, cefoxitin • Greater activity against three additional G- organisms: H. influenzae, Enterobacter aerogenes, and some Neisseria species (HENPEcK); • Activity against gram-positive organisms is weaker. • effective against Bacteroides fragilis; cefoxitin is the most potent.]

45. Pharmacodynamics • Thirdgeneration • Inferior to first-generation in activityagainst G+ cocci, • enhancedactivityagainst gram-negative bacilli • + most otherentericorganisms plus Serratiamarcescens. • Ceftriaxoneorcefotaxime • agentsofchoice in thetreatmentof meningitis. • Ceftazidime- againstPseudomonasaeruginosa. • Fourthgeneration • Cefepime, Cefpirom • onlyparenteral • Widespectrum, activeagainststreptococci and staphylococci • Not MRSA • Alsoeffectiveagainst aerobic G- organisms • e.g., enterobacter, E. coli, K. pneumoniae, P. mirabilis, and P. aeruginosa

46. Pharmacokinetics • Some orally, most IV or IM • their poor oral absorption. • All distribute very well into body fluids • adequate therapeutic levels in the CSF - only with the third-generation • ceftriaxone or cefotaxime • effective in the treatment of neonatal and childhood meningitis caused by H. influenzae • Cefazolin– • Prophylaxis in dentistry and orthopedics - ability to penetrate bone • Prophylaxis - prior to surgery because of its half-life and activity against penicillinase-producing S. aureus. • All cephalosporins cross the placenta - not teratogenic • Elimination through tubular secretion and/or glomerular filtration • dose must be adjusted in severe renal failure !!! • Biotransformation is not clinically important. • Cefoperazone and ceftriaxone - excreted in bile into the feces - frequently employed in patients with renal insufficiency.

47. Adverse effects • Allergy: • Patients who have had an anaphylactic response to PNCs should not receive cephalosporins • with caution in individuals who are allergic to PNCs - cca15 % show cross-sensitivity • In contrast, the incidence of allergic reactions to cephalosporins is 1-2 % in patients without a history of allergy to PNCs. • Disulfiram-like effect • cefamandole, cefoperazoneif ingested with alcohol or alcohol-containing medications. They block the second step in alcohol oxidation - accumulation of acetaldehyde. • Toxicity is due to the presence of the methylthiotetrazole (MTT) group • Bleeding: • agents with MTT group - because of anti-vitamin K effects. Administration of the vitamin corrects the problem. • Nephrotoxicity, diarrhea.

48. Clinical uses of the cephalosphorins • Septicaemia (e.g. cefuroxime, cefotaxime) • Pneumonia caused by susceptible organisms • Meningitis (e.g. cefriaxone, cefotaxime) • Biliary tract infection • Urinary tract infection (especially in pregnancy, or in patients unresponsive to other drugs) • Sinusitis (e.g. cefadroxil).

49. CARBAPENEMS • imipenem, meropenem, ertapenem, doripenem • Broad-spectrum including penicilase producing G+/-, anaerobes and P. aeruginosa • Administered i.v., penetrates well into CNS. • Excreted by glomerular filtration • Dose adjust in renal insuficiency • Imipenem undergoes cleavage by a dehydropeptidase • found in the brush border of the proximal renal tubuleto form an inactive metabolite that is potentially nephrotoxic - cilastatin. • Meropenem, ertapenem – not cleaved in the kidney !! • Adverse effects: • nausea, vomiting, and diarrhea • Eosinophilia and neutropenia - less common • High levels of especially imipenem may provoke seizures

50. Monobactams - aztreonam • resistant to the action of beta-lactamases • beta-lactam rings is not fused to another ring • Only P. aeruginosa and other G- bacteria • only for combination in empiric therapy. • lack of activity against gram-positive organisms or anaerobes. • IV or IM, excreted in the urine • can accumulate in patients with renal failure. • relatively nontoxic • may cause phlebitis, skin rash, and occasionally, abnormal liver function tests. • Low immunogenic potential, little cross-reactivity with antibodies induced by other beta-lactam - an alternative for patients allergic to penicillin.